As of September 2020, over 30 million COVID-19 cases and 950,000 deaths have been reported worldwide . More and more studies show that obesity and lifestyle factors, such as smoking play a role in progression and outcome of COVID-19.
Several studies showed a high frequency of obesity among COVID-19 patients admitted in intensive care . Also, disease severity increased with BMI and COVID-19 patients with grade II obesity had a higher risk of in-hospital mechanical ventilation . Lighter et al. found that obesity in COVID-19 patients younger than 60 years is a risk factor for hospital admission .
How obesity exactly influences the progression of COVID-19 is still unclear. Obesity is a major cause of type 2 diabetes mellitus, which is one of the risk factors for severe COVID-19. Diabetes is also associated with high angiotensin-converting enzyme (ACE2) expression.  Additionally, overweight and obesity have been continuously associated with a high risk of developing venous thromboembolism (VTE), a complication often found in COVID-19 patients admitted to the ICU. 
Similar results were found for COVID-19 patients that are smokers. Active smoking was associated with an increased risk of ICU admission, ventilator use and death among hospitalized COVID-19 patients. Although the exact mechanism are not clear yet, tobacco smoke can upregulate expression of angiotensin-converting enzyme 2 (ACE2), the protein used by SARS-CoV-2 as a viral receptor for cell-entry. [7, 8]
Health care professionals should take factors such as obesity and smoking into account, in order to ensure adequate treatment of COVID-19 patients.
- WHO. Coronavirus disease (COVID-19). Data as received by WHO from national authorities, as of 10 am CEST 20 September 2020 www.who.int/docs/default-source/coronaviruse/situation-reports/20200921-weekly-epi-update-6.pdf
- Magdy Beshbishy, Amany, et al. "Factors Associated with Increased Morbidity and Mortality of Obese and Overweight COVID-19 Patients." Biology 9.9 (2020): 280.
- Simonnet A, et al. High prevalence of obesity in severe acute respiratory syndrome coronavirus‐2 (SARS‐CoV‐2) requiring invasive mechanical ventilation. Obesity (2020).
- Lighter J, et al. Obesity in patients younger than 60 years is a risk factor for Covid-19 hospital admission. Clinical Infectious Diseases (2020).
- Rao S, et al. Exploring diseases/traits and blood proteins causally related to expression of ACE2, the putative receptor of SARS-CoV-2: A Mendelian Randomization analysis highlights tentative relevance of diabetes-related traits. Diabetes Care (2020).
- Lorenzet R, et al. Thrombosis and obesity: cellular bases. Thrombosis research 129.3 (2012): 285-289.
- van Zyl-Smit R, et al. Tobacco smoking and COVID-19 infection. The Lancet. Respiratory Medicine (2020).
- Kashyap VK, et al. Smoking and COVID-19: Adding Fuel to the Flame. International Journal of Molecular Sciences 21.18 (2020): 6581.